1. Field of the Invention
The present invention relates to an image processing device having the function of recognizing a specific image, an image processing method, and a storage medium in which a program implementing such a function is stored.
2. Description of the Related Art
In recent years, higher picture quality of a color copier and a printer, and higher performance of a personal computer, higher picture quality of a scanner, and the like are being realized, and a printed matter of high picture quality can be relatively easily formed. It accordingly causes a problem that securities such as paper money and various tickets which are prohibited from reproduction can be illegally reproduced by using those devices.
Aiming at mainly prohibiting such illegal reproduction, various methods of recognizing an image which is prohibited from printing by a digital image processing technique have been proposed in literatures such as Japanese Published Unexamined Patent Application Nos. Hei-6-54186, Hei-6-225134, Hei-8-335267, and Hei-9-18709. Usually, according to the techniques, a raster image is received as an input and an image prohibited from printing which exists in the raster image is recognized. Such a recognition method is convenient for a copier and the like since a read image is supplied as a raster image.
In the case of forming an image by a printer or the like, however, input image data is, for example, a drawing command and image data described in a page description language. There is consequently a problem such that the recognition method for a raster image cannot be applied as it is.
Although a raster image is created by a printer when an image is finally formed, in the case where the raster image is used for a recognition process, the created raster image cannot be outputted (formation of an image) until the recognition process is finished. It is therefore a problem that time required to form an image is long. For example, when the recognition process is performed on a raster image for printing of one page, time of ten and several to several tens seconds is required. Such long time for the recognition process is not allowed to be taken during the period from generation to output of the raster image in a higher-speed outputting device in recent years. Moreover, the resolution of an outputting apparatus is being improved and the data amount of the raster image created at the time of forming an image is increasing. The recognition process tends to take longer time as the data amount increases. It is feared that the recognition process time becomes longer as the resolution improves.